SQL Server to PostgreSQL Migration

-- SQL Server: stored procedure
CREATE PROCEDURE dbo.usp_GetTopOrders
    @CustomerId INT,
    @MaxRows    INT = 10
AS
BEGIN
    SET NOCOUNT ON;

    SELECT TOP (@MaxRows)
        o.OrderId,
        o.OrderDate,
        ISNULL(o.ShipName, 'Unknown') AS ShipName,
        o.TotalAmount
    FROM dbo.Orders o
    WHERE o.CustomerId = @CustomerId
      AND o.OrderDate >= GETDATE() - 365
    ORDER BY o.TotalAmount DESC;
END;

-- PostgreSQL: equivalent function
CREATE OR REPLACE FUNCTION usp_get_top_orders(
    p_customer_id INTEGER,
    p_max_rows    INTEGER DEFAULT 10
)
RETURNS TABLE (
    order_id     INTEGER,
    order_date   TIMESTAMP,
    ship_name    TEXT,
    total_amount NUMERIC
)
LANGUAGE plpgsql AS $$
BEGIN
    RETURN QUERY
    SELECT
        o.order_id,
        o.order_date,
        COALESCE(o.ship_name, 'Unknown'),
        o.total_amount
    FROM orders o
    WHERE o.customer_id = p_customer_id
      AND o.order_date >= NOW() - INTERVAL '1 year'
    ORDER BY o.total_amount DESC
    LIMIT p_max_rows;
END;
$$;